.test{
    width: 100px;
    height: 100px;
    color:red;
    background-image:url("./images/test.png");
}
.css {
    width: 200px;
    height: 400px;
    background-image:url("./images/haungrenxun.jpg");
}
.css-unuse {
    width: 200px;
    height: 400px;
}